Hydraulic actuator



April 24, 1962 Y J. A. HERBST 3,030,934

HYDRAULIC ACTUATOR Filed June 17, 1958 2 Sheets-Sheet 1 FIG. I F|G.'2

19a I 27 M 26 25a fig /8 A 274 I 26 i 241 FIG. 4

FIG. 3

INVENTOR. Jo fin f/Yf BY 9% 5% ATTORNEY April 24, 1962 J. A. HERBST 3,030,934

HYDRAULIC ACTUATOR Filed June 17, 1958 2 Sheets-Sheet 2 FIG. 5

FIG. 7

INVENTOR.

ATTCiRNEY United States Patent F Filed June 17, 1958, Ser. No. 742,671 9 Claims. (Cl. 121-99) This invention relates to hydraulic actuating devices.

Hydraulic actuators comprise essentially coaxially related stator and rotor members; with radial vanes on each ,to provide chambers for receiving .a hydraulic medium operative to turn the rotor member in either direction.

The vanes on both stator and rotor members are provided with seals to minimize leakage of the hydraulic medium from the high to the low pressure sides of the chambers, particularly in terms of the high pressures encountered in such devices. However, with conventional seals, the leakage is of an order which materially reduces the optimum operating efliciency of the device and results in a fairly large breakaway torque.

Accordingly, an object of this invention is to provide in hydraulic actuators, improved high pressure seals having a novel structure and manner of installation, which results in a material decrease in leakage of the hydraulic medium and a substantial reduction in the breakaway torque characteristics of the device.

In conventional seal arrangements for hydraulic actuators and motors, .the longitudinal seals on the vanes of the stator and rotor members have a sliding, rubbing engagement with opposed surface portions, as said members are assembled. Apparently, this initial frictional, rubbing action may .have an adverse effect on the sealing characteristics of such seals, which may account for the limited efliciency thereof.

In accordance with the instant invention, any longitudinal rubbing or frictional engagement of the Vans seals is avoided by initially positioning the seals in the longitudinal g ooves of the vanes in radially depressed relation to the vane edges; assembling the rotor and stator members; and after such assembly, moving the seals radially outward of their grooves into uniform, compressed sealing relation with opposed surface portions.

Furthermore, in accordance with the invention, im ,proved seal constructions are provided for disposition between the end plates of the stator and the opposed edge portions of the stator and rotor vanes, to thereby materially reduce leakage at the ends of the actuator and .to leave such end seals unimpaired and in optimum op erating condition, after the end plates are tightly secured .in place.

Other objects of this invention will in part be ob- .vious and in .part hereinafter pointed out.

In the drawings, FIG. 1 .is a transverse sectional view of a hydraulic actuator provided with seals embodying .the invention;

FIG. 2.is a partial, enlarged, transverse sectional view of a vane edge with the sealing assembly in place;

FIG. 3 is an end view of a vane showing the end sealing assembly in place;

FIG. 4 is a transverse sectional view similar to that .of FIG. :2, showing the seal assembly under conditions of use;

FIG. 5 is a partial longitudinal section showing an auxiliarysealassembly between the stator and end plates;

FIG. 6 is a partial longitudinal section showing a modified form of seal between the stator and end plates;

and

FIG. 7 is apartial longitudinal section showing a seal assembly between the rotor and endplates.

Referring in .detail ,to the drawings, It) designates a hydraulic actuator embodying the invention; the same ice comprising a cylindrical stator member 11 and a coaxial rotor member 12 rotatably mounted therein. The opposite ends of stator 11 are closed by end plates 13, 14- which have central bearing openings for passing the projecting end shaft portions I5, 16 of rotor 12.

The stator member 11 is provided with the usual radially extending vanes 17; shown as three in number for the purpose of illustration and disposed at intervals. Rotor member 12 is also provided with three radially extending vanes 18 at uniform angular intervals. As indicated in FIG. 1, vanes 18 are respectively located between vanes 17 to form chambers therebetween.

On stator member 11 there are inlets 19, 2t) for selective admission of the hydraulic medium, which may be oil, gas or water, for effecting rotation of rotor member 12 in one direction or the other, in accordance with the routing of the hydraulic medium. The end plates 13, 14 are formed with annular distribution channels 21 and passages 22 connecting correlated chambers on either side of stator vanes 17. Thus, hydraulic medium admitted by way of inlet 19 is distributed to the three successive chambers on one side of the stator vanes; while medium admitted by way of inlet 26 is distributed to the three successive chambers on the other side of said stator vanes, all in a manner known in the art.

Inasmuch as such hydraulic medium is admitted to the several chambers of the stator member under high pressure, by ptunp and valve means, not shown, the radial edges of the several vanes 17, 18 must carry sealing means to minimize the leakage of hydraulic medium from the high pressure to the low pressure sides of said chambers.

In accordance with the instant invention, longitudinal- 1y extending sealing assemblies 23 are located in longitudinal grooves 2.4 in the outer edge of vanes 18, as shown in FIG. 2; it being understood that similar sealing assemblies are on vanes 17. The vane grooves 214 are of rectangular cross section and assembly 23 comprises an outer, resilient sealing strip 25, an inner rigid metal strip 26 of rectangular cross section, and an intermediate rigid metal rod 27 of circular cross section.

The sealing strip 25 is formed of an oil resistant synthetic rubber or other suitable material; being of generally rectangular cross section and having a width to snugly fit into vane grooves 24. Strip 25- is formed on its under side with a longitudinal groove 28 of a section which provides opposed, longitudinally extending flanges 2 9 which taper to the lower edges thereof. The sides of strip 25 at the upper portion thereof may be reinforced with longitudinal, thin inserts 30 of Teflon or other suitable abrasion and oil resistant plastic.

The several elements making up seal assembly 23 are mounted in vane grooves 24, as follows. The strips 25 and 27 are located in said grooves, before or after the assembly of the rotor and stator members. Since the combined thickness of strips 25, 27 is less thanthe depth of grooves 24, the outer surface of strip 2-5 will be depressed below the edge 18a of vane 18. Thus, the outer surface of said strip 25 will not be abraded or otherwise disturbed as an incident to the location of the strip 25 in grooves 24.

With the stator and rotor members in assembled, coaxial relation, sealing strips 25' are brought into their operative positions. To this end, strip 26 is inserted endwise into groove 24 beneath rod 2 7 and moved longitudinally in the groove to its proper position within the groove. As a consequence, sealing strip 25 is moved radially outward of vane grooves 24 into contact with the opposed rotor surface .31 or the stator bore 32. As the combined thickness of the rod 27, strip 26 and sealing strip 25 in its uncompressed condition, is greater than the depth of vane grooves 24, it follows that sealing strip 25 will be under uniform radial compression throughout the length thereof, thereby effecting a tight seal in respect to the opposed rotor or stator surface portions.

By proper selection of the thickness dimensions of strips 25, #26 and rod 27, the extent of compression of strip 25 may be controlled. The ends of vanes 17, 18 may also be grooved to receive short seal assemblies 23 which will lie in opposed relation to end plates 13, 14. Thus as shown in FIG. 3, seal strip 25a, rod 27a and strip 26a will be located in vane groove 24a and strip 25a will be compressed when the end plates 13, 14 are bolted in place on stator 11.

It has been found that with seal assemblies 23, as described, and their manner of installation without abrasion or other disturbance of the outer surfaces of seal strips 25, a substantial increase in effectiveness of the seal between the high and low pressure chambers formed by vanes 17, 18, is attained and leakage is markedly reduced. In addition, breakaway torques are reduced.

Apparently, the sealing efficiency of assemblies 23 may be attributed in part, to the tapered flange portions 29 on seal strips 25. Thus, as indicated in FIG. 4, assuming that the chamber to the right of vane 18 is the high pressure side and that to the left of said vane is the low pressure side; such pressure differential will deform seal strip 25 to provide a channel connecting the high pressure chamber with groove 24 and to admit hydraulic medium into said groove with a resultant pressure applied to the left hand tapered flange portion 29, urging said flange portion into intimate contact with the opposed wall surface of groove 24. In this manner, leakage by way of the vane grooves is substantially eliminated.

To further insure optimum sealing at the joints of the hydraulic actuator 10, improved seals are provided between the stator 11 and end plates 13, 14, as indicated in FIGS. 5, 6; and between the rotor 12 and said end plates, as indicated in FIG. 7.

Thus, as shown in FIG. 5, the bore 32 of stator 11 is slightly extended at its ends beyond the ends of rotor 12. The end plate 13 is formed with a bolting flange 33 and is stepped on its inner surface, as at 34, 35, forming an annular shoulder 36 which is provided with an annular groove 37 for the purpose hereinafter appearing.

An annular sealing ring 38 of normally rectangular cross section is mounted on step 35, said ring having a normal thickness slightly less than the depth of said step. On bolting end plate 13 in place on stator 11, the outer portion of step 35 will move into bore 32 to compress ring 38 between shoulder 36 and the opposed shouldered portion of said stator, to produce an effective seal at the joint between stator and end plate. Since compression of the resilient ring 38 results in the formation of a pinched or protuberant portion of said ring; groove 37 is adapted to receive said pinch or protuberance without shearing or otherwise impairing the ring 38.

Furthermore, while step 35 on end plate 13 may be turned to have a tight sliding fit with stator bore 32; preferably, said step is turned to have a loose fit and a coating of epoxy resin 39 is applied to the step. Coating 39 is sheared somewhat when end plate 13 is bolted in place, thus insuring a tight fit between the assembled parts. The same procedure is applicable to end plate 14.

Alternatively, as shown in FIG. 6, end plate 13a may be formed with a single step 34a having a communicating annular groove 40 for receiving a resilient sealing ring 41. Furthermore, the annular edge of step 34a is bevelled as at 42. Thus, when plate 13a is bolted in place on stator 11, stepped portion 34a is received in recess 43 on stator 11 and bevelled edge 42 abuts and compresses resilient sealing ring 44 in stator recess 43. Ring 44 is deformed on compression and may flow laterally within the recess by reason of the triangular shaped space defined by said recess and bevelled edge 42, avoiding pinching or shearing of said ring 44.

Leakage at the shaft ends 15, 16 of rotor 12 where the same pass through the bearing openings in end plates 13, 14, is materially reduced by the seal construction shown in FIG. 7. Thus, the usual bearing lining 45 is of reduced axial extent to provide an annular groove of rectangular cross section on the inner face of end plate 13. An L-shaped annular ring 46 of bearing metal is located in said groove; said bearing metal ring 46 in turn supporting an annular resilient seal 47, also of L shaped section.

The resilient seal 47 is disposed in opposed relation to shoulder 48 of rotor shaft 15, the bearing metal ring 46 being spaced therefrom to allow for compression of seal 47 when end plate 13 is bolted in place. The bearing metal ring 46 is formed with an annular groove 49 to receive protuberant portions of resilient seal 47 under compression, thereby avoiding pinching or shearing of said seal.

Preferably, a split metal ring 50 is seated on resilient seal 47 to provide a smooth bearing surface for the lower ends of seal 25a on the vanes 18 of rotor 12. It is understood that shaft end 16 is similarly sealed, as indicated in FIG. 7. All resilient seals are formed of oil resistant, synthetic rubber.

It will be apparent that the vane and end plate seals described herein, taken singly or in combination, are effective to sharply reduce leakage of hydraulic medium under the high pressures encountered in hydraulic actuators, so as to substantially increase the operation efliciency of the device.

As various changes might be made in the embodiments of the invention herein shown and described without departing from the spirit thereof, it is understood that all matter herein shown or described shall be deemed illustrative and not limiting except as set forth in the appended claims.

Having thus described my invention, 1 claim as new and desire to protect by Letters Patent:

1. A hydraulic device comprising a cylindrical stator member, a rotor member rotatably mounted in said stator member and providing an annular space between said members, a plurality of vanes extending between said members in said annular space, each of said members having at least one vane fixed thereon and extending radially to the opposed surface portion of the other member, means for sealing the outer edge of each vane comprising an elongated sealing assembly and an elongated groove formed in the outer edge of each vane to receive said assembly, said assembly comprising an outer, compressible strip, an elongated pressure transmitting member abutting inner surface portions of said compressible strip, and an elongated pressure applying member adapted to be inserted into said groove while said compressible strip and pressure transmitting member are in place within said groove for abutting said pressure transmitting member and uniformly exerting radial pressure throughout the length of said groove to bias said compressible strip radially outward of said groove into sealing contact with the opposed surface of one of said members.

2. A device as in claim 1 wherein said compressible member has a longitudinal groove on the inner surface thereof and said pressure transmitting member is of circular cross section received in the groove of said compressible strip.

3. A device as in claim 2 wherein said compressible member comprises laterally spaced, longitudinally extending tapered edge portions on either side of the groove therein.

4. For use in a hydraulic device having vanes and surface portions in opposed relation to the outer edges of said vanes with relative movement therebetween, sealing means for said vanes comprising a sealing assembly and a groove formed in the outer edge of said vanes for receiving said assembly, said assembly comprising an outer compressible element, an intermediate pressure transmitting element and an inner pressure applying element, said outer and intermediate elements having a combined thickness less than the depth of said groove, said outer, intermediate and inner elements having a combined thickness while said outer element is uncompressed greater than the depth of said groove, said inner element being separable from the other elements and adapted to be intro duced into said groove for contacting said intermediate element and biasing said outer element radially outward of said groove whereby to compress said outer element against an opposed surface portion.

5. In a hydraulic actuator having coaxially related stator and rotor members, each of said members having radially extending vanes formed with sealing grooves on the edges and ends thereof, and end plates on said stator member for rotiatably mounting said rotor member, sealing means for said vanes comprising compressible sealing strips disposed in said vane grooves and rigid means insertable into said grooves for contact with the underside of said sealing strips for biasing said sealing strips outward of said grooves, each of said rigid means and the associated sealing strip in its uncompressed condition having a combined thickness greater than the depth of said groove whereby to urge said strips into operative sealing position.

6. In a hydraulic actuator having a plurality of vanes and surface portions in opposed relation to the edges of said vanes, said vane edges being formed with longitudinal grooves to receive sealing assemblies, each sealing assembly comprising *an outer resilient sealing strip and a rigid member within said groove and in contact with the underside of said strip for biasing said strip outwardly of said groove, said rigid member and said sealing strip in an uncompressed condition having a combined thickness greater than the depth of said groove whereby to urge said strip into sealing relation with said opposed surface portions, said sealing strip being formed with a longitudinal groove on the under side thereof to provide 6 laterally spaced tapered edge portions for sealing engagement with the respective side walls of said groove upon lateral compression of said sealing strip and the admis sion of hydraulic medium into said groove.

7. For use with the vanes of a hydraulic actuator wherein said vanes are formed with grooves to receive sealing means, a sealing assembly for disposition in said vane grooves comprising an outer resilient sealing strip, an elongated rigid intermediate member and a rigid elongated inner member, the combined thickness of said intermediate member and the uncompressed resilient memher being less than the depth of said groove, and the combined thickness of said inner member, intermediate member and the uncomprmsed resilient member being greater than the depth of said groove.

8. A sealing assembly as in claim 7 wherein said outer strip is of generally rectangular cross section, said intermediate member being of circular cross section and having tangential contact with an under surface portion of said strip, and said inner member has a flat surface for tangential contact with said intermediate member.

9. A sealing assembly as in claim 8 wherein said outer stnip is formed with a longitudinal groove on the under surface thereof, said intermediate member having a peripheral portion received within said groove.

References Cited in the file of this patent UNITED STATES PATENTS 2,164,876 Horlacher July 4, 1939 2,339,042 Anderson Jan. 11, 1944 2,377,674 Chisholm June 5, 1945 2,778,338 Shafer Jan. 22, 1957 2,781,027 Henry Feb. 12, 1957 2,793,623 Ludwig et al. May 28, 1957 2,798,462 Ludwig et al. July 9, 1957 2,811,142 Shafer Oct. 29, 1957 

